MOLECULAR MECHANISM OF NDP KINASE A IN TUMOR METASTASIS

该项目的长期目标是了解人类NDP激酶A(NDPK-A)是如何参与肿瘤转移的，肿瘤转移是癌症患者死亡的主要原因。NDPK-A水平升高与神经母细胞瘤的高转移潜能密切相关。提示NDPK-A可能是该肿瘤的转移促进剂。此外，我们在26%的转移性神经母细胞瘤患者中检测到Ser120产生NDPK-A的甘氨酸突变。虽然已知NDPK-A作为磷酸转移酶参与核酸代谢，但这种酶活性与肿瘤转移无关，提示NDPK-A在肿瘤进展中还有其他功能(S)。事实上，我们的初步数据表明，NDPK-A在体外可以通过与c-myc基因中的顺式作用元件结合并激活c-myc转录来发挥转录因子的作用。我们推测NDPK-A通过下调c-myc转录促进神经母细胞瘤的转移。在神经母细胞瘤细胞和SCID小鼠模型系统中，我们提出了五个特定的目标来检验这一假说的各个方面：(1)检查NDPK-A的蛋白质水平和结构的变化是否影响NDPK-A的核定位。(2)检测NDPK-A蛋白水平和结构的改变是否增强细胞生长和侵袭力。(3)检测表达NDPK-A蛋白水平和结构改变的神经母细胞瘤细胞是否促进SCID小鼠肿瘤的形成和转移。(4)体内研究NDPK-A对c-myc转录的调控作用。(5)阐明NDPK-A调控的潜在靶基因。拟议的体外和体内研究结果将确定NDPK-A是否促进神经母细胞瘤的转移。结果可能指向一个或多个特定的细胞过程，这些过程受到NDPK-A蛋白水平和结构变化的影响。我们还将获得有关NDPK-A放松c-myc转录调控的新信息。此外，识别NDPK-A识别的一致序列将有助于识别其潜在的靶基因，并扩大我们对NDPK-A网络的理解。

The long-term goal of this project is to understand how human NDP kinase A (NDPK-A) is involved in tumor metastasis, a major cause of death in cancer patients. An increased NDPK-A level is strongly correlated with high metastatic potential of neuroblastoma. This suggests that NDPK-A may be a metastasis promoter in this cancer. In addition, we have detected the Serl20 yields Gly mutation of NDPK-A in 26 percent of patients with metastatic neuroblastoma. Although NDPK-A is known to function as a phosphate transferase and participate in nucleic acid metabolism, this enzymatic activity is not correlated with tumor metastasis, suggesting other function(s) of NDPK-A in tumor progression. In fact, our preliminary data demonstrate that NDPK-A can function as a transcription factor in vitro by binding to a cis-acting element in the c-myc gene and activating c-myc transcription. We hypothesize that NDPK-A promotes the metastasis of neuroblastoma by deregulating c-myc transcription. Five specific aims are proposed to test facets of the hypothesis in neuroblastoma cell and SCID mice model systems: (1) Examine if alterations in the protein level and structure of NDPK-A affect nuclear localization of NDPK-A. (2) Examine if alterations in the protein level and structure of NDPK-A enhance cell growth and invasiveness. (3) Determine if neuroblastoma cells expressing an altered protein level and structure of NDPK-A promote tumor formation and metastasis in SCID mice. (4) Study the deregulation of c-myc transcription by NDPK-A in vivo. (5) Elucidate the potential target genes which are regulated by NDPK-A. Findings from the proposed in-vitro and in-vivo studies will establish whether NDPK-A promotes the metastasis of neuroblastoma. The results may point to one or more specific cellular processes that are affected by alterations in the protein level and structure of NDPK-A. We will also obtain new information regarding the deregulation of c-myc transcription by NDPK-A. Furthermore, identification of the consensus sequence recognized by NDPK-A will allow the identification of its potential target genes and expand our understanding of the NDPK-A network.